Next-generation photonic power electronic systems based on optically-triggered devices (OTDs) provide key advantages over conventional, electrically-triggered devices (ETD) based switching power systems. For example, optical switching enhances the possibility of system integration by reducing the problems associated with electromagnetic-interference (EMI) effects. Further, for an optically-triggered (OT) converter, designs of high- and low-side drivers can remain the same, yielding simple design, enhanced reliability, and monolithic integration. By contrast, for two- and higher-level electrically-triggered (ET) switching converters, different designs of low- and high-side drivers are required; the latter is especially difficult to design for medium and high-power applications. Optical triggering also provides the possibility of optically modulating (by varying the properties of the optical signal for example intensity, wavelength, etc.) the radiated/conducted electromagnetic signature of a power electronics system. Optical triggering further provides possibility of controlling the efficiency of the power electronics system dynamically. Additionally, owing to the direct photogeneration, which introduces very short delay, optical triggering enables synchronized operation of series/parallel connected array of power devices. This may enable creating series/parallel connected switch assembly for scaling up the voltage blocking or current carrying capability, which is, otherwise, not possible with a single power device in existing technology.
Additionally, unlike an OTD, as the switching frequency of an ETD increases, parasitic oscillations may be induced in the driver circuit owing to coupling effects because of the device capacitance and the parasitic inductance of the gate connection, and to transmission-line effects. Also, in an OTD, there is complete isolation between the gate driver and the power stage. As such, very high di/dt and dv/dt, which cause significant reliability problems in an ETD at a high switch frequency, have no impact on an OTD. Therefore, the basic architecture of the gate driver in an OTD is simple. Still further, an OTD-based converter does not suffer from gate-driver failure due to short-circuiting.
Additionally, recent research has shown that tangible reductions in weight, volume, and cost are possible through an application of emerging photonic technologies for air, land, or sea based vehicle power management systems, such as those based on fly-by-light (FBL) architecture. An electrically isolated flight control mode based on photonic technology could provide a lightweight, EMI resistant system.
However, to realize such photonic power electronics, device technologies, that address several key issues, are needed. One such issue is wavelength of operation from the standpoint of trade-off between cost, optical absorption and technical complexity of the optical source. Another issue is electrical gain. To reduce the power requirements, volume, and weight of the optical triggering source, high electrical (device) gain and quantum efficiency are desirable. A further issue is switching speed. A fast turn-on and turn-off of the OTD along with low on resistance is needed to efficiently support high-frequency repetitive switching in power electronics. A low-loss rapid switching capability also enhances the power density of the power system, which is desirable for most applications. Yet another issue is high-temperature operability. High-temperature operability is often required to address the robustness of the power converter and high power density.
Light-triggered thyristors and optothyristors are two known examples of photoconductive power devices designed for power electronics. However, both of these known devices feature an inherent thyristor-like latch-up problem, leading to uncontrollable and slow turn-off, which is not desirable for a fast repetitive switching device.
Moreover, vertical devices like optothyristors employ a semi-insulating thick layer instead of a controllably doped layer. This results in a large voltage drop across the device during conduction. For switching devices in power electronic applications, this drop is unacceptable from an efficiency point of view, and the voltage-sustaining layer must be doped controllably so as to maintain an optimum balance between on-state conduction drop and off-stage voltage blocking capability.